The field of the present invention is directed principally to apparatus and systems for resisting or preventing the collapse of mine roofs and adjacent material in the sides thereof so as to stabilize such formations. Several types of mechanical and grout anchors have been used in the past to improve the anchorage of mine roof support means and to provide long term stability to the system. Mechanical drive anchors have been used at the top of the anchorage drive points on the cable, and these drive anchors are so designed that they may expand in the bore holes to secure tight anchorage in the rock mass.
A mine roof support system is disclosed in the patent of C. C. White U.S. Pat. No. 3,505,824 issued Apr. 14, 1970, and in this system a series of bent rods are utilized in which the opposite end portions of the rod system is secured in a bore hole and turnbuckle type tension means is applied to the exposed ends in the mine passage. A further application of a rod system for mine passage roof support is disclosed by C. C. White in U.S. Pat. No. 3,509,726 of May 5, 1970. An earlier mine roof support system employing flexible cables is disclosed by C. C. White in U.S. Pat. No. 3,427,811 of Feb. 18, 1969. In this disclosure rod anchor elements are disposed in bore holes in the mine roof and the exposed ends are interconnected by a flexible cable arrangement utilizing a turnbuckle device for imposing tension in the rod-cable system combination. Galis disclosed in U.S. Pat. No. 3,601,994 of Aug. 31, 1971 a roof support system for underground mines having a flexible cable arrangement in which the opposite ends of the cables were anchored by wedging members exerting restricted contact in the surface of the bore holes after the wedging members are driven home to apply desired tension on the cables.